Since nobody has mentioned it yet, KOReader is an open source reader application for ereaders, kindles & others, and has the ability to reflow PDF's. While not perfect, it can work good enough to read well formatted PDF's.
Kindles need to be jailbroken to use koreader, and Amazon apparantly makes that harder with each device :-/
I have this as a right-click action for files matching *.pdf in my file browser (thunar):
k2pdfopt -ui- -dev kp3 %F
(%F is the quoted file name, in your terminal you would `k2pdfopt -ui- -dev kp3 'something.pdf'`)
Alternative phrasing: Amazon is continuing to fix security bugs in Kindle device.